JPH04132004A - Method and device for testing optimum writing current for magnetic disk storage device - Google Patents

Abstract

PURPOSE:To test the optimum value of a data writing current for the quality control of a magnetic disk storage device in form conforming with a mass-produced device by carrying automatically an optimum writing current test by the device itself in the form conforming with its read-write characteristic while using a head and a circuit to read and write actual data. CONSTITUTION:Prescribed test data is written while the writing current of the data is kept at a prescribed value, and in addition, the head 3 is kept in an on-track state to the tack of a disk 1. Then, after approving the pressure of an error of reading by reading the test data every time the head 3 is turned into the on-track state and the off-track state to the track, the total sum of the number of times of the error of reading is stored correspondingly to the writing current, and the writing current corresponding to the minimum number of times among the numbers of times of the error of reading stored for every value of the writing current while changing the writing current within a prescribed range is selected as the optimum writing current value. Thus, the writing current can be set at the value conforming most with the actual condition of the magnetic disk storage device by using the head and the circuit for actual read-write and testing it in the form including the over-all characteristic of the device related to the read-write of the data, and the optimum writing current test can be automatically carried forward.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a method for testing the optimum value of write current to be applied to a head when writing data to a disk of a magnetic disk storage device such as a fixed disk device. METHODS AND APPARATUS.

[Conventional technology]

As is well known, in magnetic recording, data is written by magnetizing the magnetic medium of the disk using a magnetic field generated by passing a current through the coil of a transducer such as a head.
The magnitude of the write current at this time greatly influences the magnetic recording characteristics of a predetermined code pattern representing data.

That is, if the write current is too small, magnetic recording will of course become uncertain, but if the write current is too large, the resolution in recording the code pattern will deteriorate.

Furthermore, in reality, it is not only simple recording (data is overwritten or overwritten), so it is important to set the write current so that the previous data is not left unerased.

For this reason, although the materials and manufacturing methods of the magnetic recording media used in disks differ, precise magnetic property tests have traditionally been conducted before incorporating them into disk storage devices, and write currents of various magnitudes have been tested. It has been customary to set the write current to a value Wr that is determined to be comprehensively optimal based on the results of evaluating the resolution and overwrite characteristics of the magnetic medium. Furthermore, since the magnetic properties of the medium are easily affected by temperature, it is desirable to determine the final setting of the write current based on comprehensive judgment based on the results of evaluation tests conducted under at least two different temperatures.

[Problem to be solved by the invention]

As mentioned above, by precisely evaluating the magnetic properties of various magnetic recording media in advance, it should be possible to set the optimal write current value for the disk storage device. When we sampled a few sides for management purposes and checked the validity of the write current, we found that the settings were not necessarily ideal.

Of course, part of the reason for the second reason is that the magnetic recording characteristics of the media can vary slightly from manufacturing lot to manufacturing lot, but detailed investigation results show that the influence of fluctuations in the data read/write characteristics of the head is actually greater. Understood. In particular, in fixed magnetic disk drives, the heads are floated aerodynamically, so -
It is conceivable that the optimum value of the write current may deviate due to slight variations in the flying characteristics due to the characteristics of the spring that supports it. In addition, due to variations in the signal processing characteristics of the data reading circuits of each magnetic disk storage device, and also due to the code pattern method used in magnetic recording of data, the write current setting may deviate slightly from the optimal value. There is.

From this, it can be seen that it is desirable for quality control to set the write current at least for each loft when mass producing magnetic disk storage devices, but it is impractical to precisely evaluate resolution and overwrite characteristics as has been done up until now. lacking in
Furthermore, it is extremely difficult to evaluate these by changing the temperature in terms of the time and effort required.

Based on such circumstances, it is an object of the present invention to provide a method for easily testing the optimum data write current for quality control of magnetic disk storage devices in a manner suitable for mass-produced devices.

[Means to solve the problem]

In order to solve this problem, the optimum write current test method for magnetic disk storage devices according to the present invention writes predetermined test data while keeping the data write current at a predetermined value and keeping the head on track on the disk. The test data is read each time the head is turned on and off track relative to the track, and the presence or absence of a read error is verified.The total number of read errors is stored in correspondence with the write current value, and the write current is This problem can be solved by changing the value within a predetermined range and selecting the write current corresponding to the lowest number of read errors stored for each value as the optimum write current value.

Note that it is preferable that the above test data be written by overwriting after writing predetermined data, for example, data with the lowest writing frequency.

Moreover, above! ! l! According to the optimum write current testing device for a magnetic disk storage device of the present invention, l is a write current adjustment circuit that adjusts the current value for writing data to a track in the disk via the head, and this write current adjustment circuit. a write current specifying means for specifying a write current; a head position control means capable of controlling the head position with respect to the track; and a write current specifying means specifying a write current with the head on track by the head position control means. A test data writing means writes test data using a write current, and a head position control means turns the head on and off track with respect to this track, and then reads the test data to check for read errors while checking for read errors. The reading test means counts the number of reading errors and stores the sum of the number of reading errors, and the writing current specifying means switches the write current of the test data while the reading testing means calculates the number of reading errors each time. This problem can be solved by storing the sum and selecting the write current corresponding to the lowest value among the stored values as the optimum write current.

Note that the write current adjustment circuit described above is composed of a series circuit of a plurality of write resistors and a switch connected in parallel to each write resistor, and a write current designation code of multiple bits is output from the write current designation means. It is advantageous to provide this with a corresponding switch depending on the content of each bit.

[Effect]

The present invention allows each magnetic disk storage device to automatically perform an optimum write current test using the head and circuitry that actually reads and writes data using its own code pattern method, using the device itself and in accordance with its reading and writing characteristics. This solves the above-mentioned problems by making it possible to proceed in a consistent manner.

Therefore, in the present invention, test data is written in a predetermined code pattern method while the write current is kept at a predetermined value and the head is on-track, and then this test data is read through the head to check for read errors. After verification, the number of reading errors is stored in correspondence with the write current value, and this operation is repeated without sequentially changing the write current.

At this time, by reading the test data written at each write current value not only in the on-track state of the head but also in the off-track state, the resolution of the code pattern recording of the magnetic recording medium at that current value can be adjusted for the device. After evaluating the current value in a sensitive and realistic manner, including the characteristics of the head and circuit, the number of reading errors for that current value is stored in the form of the sum of the number of errors in both states.

Furthermore, evaluation tests can be carried out by writing test data at each write current, for example after writing the data with the lowest write frequency, or by repeating writing and reading test data multiple times by switching the data content. This can be done in a manner that includes the overwrite characteristics of the magnetic recording medium in terms of current value.

After repeating this operation while sequentially switching the write current within a predetermined range, the optimal write is performed by selecting the write current value corresponding to the lowest number of read errors stored for each write current value. It can be easily determined as a current.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a configuration example of a fixed magnetic disk device as a magnetic disk storage device 90 embodying the present invention.

The disk l shown in the upper left of the figure is the spindle motor 2
is driven at a constant speed. The head 3 provided on each side of the disk 1 is supported by a swinging arm 4 as shown in the figure, for example, and is driven by an actuator 5 such as a voice coil motor.
Its position is manipulated by Note that positioning of the head 3 on each track is carried out as usual on the disk 1.
While reading the servo information written in the servo information in synchronization with the index pulse 1χ generated by the pulse generator 2a of the spindle motor 2, the head position control means 50 (described later)
This is done by controlling the actuator 5 from there through its drive circuit 5a. Furthermore, all the disk drives 3 in the magnetic disk storage device ff19G are connected to the read/write circuit 6 via flexible leads or the like, as shown by thin lines in the figure.

This read/write circuit 6 is normally built into a magnetic disk storage device 80, and puts the head 3 designated by the head selection command Is into a reading state or a writing state in accordance with a read/write command R- (as well as a read/write signal). R5 and the write signal WS are amplified, and in the context of the present invention, a write current adjustment circuit 30 is connected thereto.

The read/write circuit 6 has a current setting terminal, and the head 3
Since the write current flowing through the circuit can be set by the value of the resistor connected to it, the write current adjustment circuit 30 can be configured by, for example, as shown in FIG. Switches 35 such as transistors connected in parallel
For example, a 3-bit current designation code i is given to this, and the switch 35 is set according to the value of 0 to 7.
It is convenient to selectively open and close 37.

The read signal R5 outputted from the read/write circuit 6 is given to the data circuit 1O via the demodulation circuit 7, the data S circuit 8, and the encoder/decoder circuit 9 as in the previous example.

The data circuit IO is a small processor dedicated to data, and receives the read signal R5 from the encoder/decoder circuit 9.
is converted into digital data and placed on the internal bus 12,
Or conversely, data is read from the internal bus 12, converted into a write signal -3, and then provided to the read/write circuit 6 via the encoder/decoder circuit 9. It temporarily stores a track's worth of test data, verifies the presence or absence of reading errors, and counts the number of errors.

In addition, a processor 11 is incorporated in the magnetic disk storage device 90 for overall control thereof, and an internal bus 12.
It is connected to a computer via an interface circuit 13 and an external bus 14, and is also connected to a data circuit IO via a communication bus 15.

Further, an off-track detection circuit 20 is specifically incorporated in the magnetic disk storage device 90 in this embodiment, and the read signal 1? The off-track amount d from the center of each track of the head 3 is detected from the read portion of the servo information.

Now, when performing the optimum write current test according to the present invention, the above-mentioned write current adjustment circuit 30 is connected to the processor 11 via its output port, etc., and the write current specifying means 40 and the head position control means 50 are tested. Both the data writing means 60 and the reading test means 70 are loaded in the processor 11 in the form of software as shown in the figure, and the test automatically proceeds by operating these means. In connection with this operation, it is convenient to use an indicator light 16 such as an LED built into the magnetic disk storage device 90, or to temporarily connect it during the test.

Hereinafter, the overall operation of the present invention will be explained with reference to an example of the operation of these means 40 to 70 shown in FIG. In addition, the operation of each means is shown surrounded by a dashed-dotted line in the figure. The optimum write current test is performed, for example, on a magnetic disk storage unit taken out of a loft after assembly for the purpose of product control during mass production. After erasing the entire surface, the illustrated flow is activated.

After the start of the test, the write current specifying means 40 is activated,
In the first step 41, 0 is set in the variable i for the current designation code, and in the next step 42, this value is output to the write current adjustment circuit 30 and the switches 35 to 37 in FIG.
For example, by turning off all of the write current to be applied to the head 3 when writing test data is set to the lowest value. In addition, these switches allow short-circuitable low resistance 3
The values of 2.33.34 are set to a ratio of 1, 2.4, for example, and the write current is set to the value of the high resistance 31 and the value of the three low resistances 32 to 34 according to the value of the 3-bit current designation code i. specified within the range of variation determined by the ratio of the total resistance values of

The flow after this starts with the operation of the test data writing means 60.

In this embodiment, the test data is always written by overwriting, so in the first step 61, the test data T
The data to be erased DO is designated as D. This data to be erased DO is preferably data with the lowest writing frequency, for example, and if the data recording method is 1/7 code of the RLL method, 88 hide data are repeated.

Also, in this step 61, the flag F for controlling the subsequent flow is set to 1, and in the subsequent step 62, the read/write command R@ to the read/write circuit 6 is set to 0, the head 3 is placed in the reading state, and the flow is controlled by the head. Position control means 5
Put it in 0.

The operation steps 51 to 54 of the head position control means 50 are for bringing the helad 3 on track. In the first step 51, the index pulse ■χ is waited for, and at the same time as the arrival, the operation is shifted to step 52. , the zero-order step 53 of reading the off-track amount d from the off-track detection circuit 20 is to determine whether the value of this off-track amount d is smaller than its permissible limit d-, and if not, the following step 54 The actuator 5 is driven by the drive circuit 5a.
, the position of the head 3 is corrected so that the off-track amount d becomes 0, and the flow returns to step 51 to repeat the same operation. 3 is or becomes on-track, the operation moves to step 63 of the test data writing means 60.

In the second step 63, the read/write command ■ is set to 1 to put the head 3 into the writing state, and in step 61
A write signal -5 of the test data DO specified in is given to the head 3 from the data circuit IO via the encoder/decoder circuit 9 and the read/write circuit 6, and writing with the specified write current is started in step 42. . Step 64 is for waiting for the arrival of the index pulse 1χ, and when the index pulse 1χ arrives, writing of the data to be erased Do to the track is completed. In the following step 65, it is checked whether the flag F is 0 or not, but since it is now a work period, the operation moves to step 66.

From this step 66, the process moves to writing the true test data, puts 1 in the test data number j, returns the flag F to 0, and then writes the number of reading errors c+ corresponding to the current designation code i.
In the first step 67, the test data DT is placed in t-o.
Specify the P-jth test data Dj 0 In implementing the present invention, it is desirable to specify 2 to 3 so-called pad pattern data that are difficult to read in the test data, and the test data number j specifies these sequentially. It is for.

After step 67, the flow returns to step 62 to cause the head 3 to be on-track again by the head position control means 50, and after writing the above-mentioned test data Dj to the trunk in steps 63 and 64, the operation is continued. 65, but since the flag F has returned to O this time, the flow begins to operate as the reading test means 70.

In the first step 71, the read/write command R is first read/written.
Specify that the reading test should be started with the head turned offtrunk in the negative direction by setting - to 0 to put the head 3 in the reading state, then put -δ in the target value da for the off-track amount d. do. In this embodiment, the reading test is performed in three states: an on-track state and a positive and negative off-track state. Note that the value of δ above for off-track is 2 to 3 when the inter-track pitch is about 10a.
After this step 71, the operation is shifted to the operations of the stainless steels 155 to 58 as the head position control means 50 in order to position the helad 3 at the off-track target value da.

In the first step 55, the index pulse IX is waited for, and at the same time as the index pulse IX arrives, in step 56, the current off-track amount d is read from the off-track detection circuit 20, and the deviation dd from the target value da is determined. In the following step 57, it is checked whether the value of this deviation dd is smaller than the allowable limit d-, and as long as it is not, in step 58, the position of the head 3 is corrected to make the deviation dd 0 in the same way as described above. When the head 3 is positioned at the target value da, the operation moves from step 57 to step 72 of the reading test means 70.

In this step 72, the test data TO, that is, the j-th test data Oj previously designated in step 67, is read into the data circuit 10. The data circuit 10 reads this test data Dj, verifies the presence or absence of a reading error as described above, and counts the number of reading errors, so the reading testing means 70 waits for the index pulse IX in the next step 73, and then Synchronously, in step 74, the number of reading errors Cj for the j-th test data DJ is read from the data circuit 10 and added to the above-mentioned reading number variable Ci.

In the next step 75, it is checked whether the off-track target value da has reached δ, and if not, in step 76, the target value d1 is moved by δ and the flow returns to step 55.
Therefore, this time, with head 3 on track,
Further, next, the same operation as described above is repeated with off-tracking in the positive direction by δ. When the reading test for the first test data Dj in the on-track and positive/negative off-track states is completed, the operation proceeds to step 7.
5, the process moves to step 68 of the test data writing means 60.

In this step 68, it is checked whether the test data number j has reached the planned quantity large value j-, and as long as it is not, the process returns to step 6.
At step 9, the test data number j is deleted, and the flow returns to step 67 to designate the new test data Dj as the test data TD. Thereafter, the operation returns to step 62, and the same operations as above for the test data writing means 60 and reading test means 70 are repeated. When the test data Dj is sequentially switched in this way and the operation for the maximum value ja of the number j is completed, the flow moves from step 68 to step 77 of the reading test means 70.

The number of reading errors Ci that has been sequentially added in step 74 up to this point includes js pieces of test data sequentially written by overwriting with the write current corresponding to the current designation code i, respectively on track and positive and negative off track. The total number of reading errors resulting from reading in this state is stored.

In step 77, this value is stored in correspondence with the value of current designation code 5.

The subsequent operation is moved to step 43 of the write current designation means 40, where it is determined whether the value of the current designation code i at that time has reached its maximum value, 7 in this embodiment, and the answer is NO. In the next step 44, the value of i is changed and the flow returns to step 42, thereby repeating the same operation as before with the write current specified by the new current specification code i.

In this way, the test is repeated while the current specification code i is successively incremented, and when the test at the maximum write current specified by the maximum value i- is completed, the flow proceeds to step 43.
Then, the operation loop up to now is extracted and the process moves to step 81.

Second step 81 to step 85 are for finding the value of the current designation code i corresponding to the lowest value among the in reading error counts Ci stored up to that point.

In step 81, the current designation code i is set to 0, and a sufficiently large value 0 is set to the minimum number of reading errors C. In step 82, it is checked whether the stored value of the number of reading errors Ci corresponding to the current designation code i is smaller than the minimum number of reading errors C. If not, the operation moves to step 84; Input the former value into the latter, and enter the value of the current designation code i into the optimum current designation code in. In step 84, it is checked whether the value of i is smaller than the maximum value is, and as long as the value of i is exceeded in step 85, the operation is returned to step 82 and the same operation is repeated.

When the current specification code i reaches the maximum value of 1, the value of the minimum number of reading errors C among all the number of reading errors C3 and the corresponding optimum current specification code in are known, so in step 86 these are Storing the value terminates the entire operation of the optimum write current test of the present invention.

The results of the optimal write current test according to the present invention explained above are as follows:
For example, it is very convenient in practice to display the indicator light 16 in Fig. 1 by lighting it up according to the value of the optimum current designation code in. In addition to in and C, the number of reading errors Ci corresponding to each current designation code i can be recorded.

In either case, the write current value can be reasonably set for each magnetic disk storage device or its lot based on the optimum write current test results. Although the number of operation steps in the optimum write current test shown in FIG. 3 is quite large, the actual test time is short enough not to cause problems during mass production, and since it is an automatic test, almost no effort is required.

In the embodiment shown in Fig. 3, the steps for switching and moving the heads are omitted to avoid unnecessary complications, but in reality, the heads are sequentially placed on multiple tracks on the disk, and the heads are switched. However, it is desirable to test multiple disk surfaces.

In addition, if necessary, the optimal write current test is performed under multiple temperatures, although it takes some time.In this case, the optimal write current value may differ depending on the temperature, but the It is preferable to determine the optimum write current value by comprehensively judging from the recorded value of the number of reading errors for each current designation code.

〔Effect of the invention〕

As described above, in the optimum write current test for the magnetic disk storage device of the present invention, predetermined test data is written while the data write current is kept at a predetermined value and the head is kept on track on the disk. The test data is read each time with the HEAD on and off track for this track, and the presence or absence of reading errors is verified.The total number of reading errors is stored in correspondence with the write current value, and the data is written. By changing the write current within a predetermined range and selecting the write current corresponding to the lowest number of read errors stored for each value as the optimum write current value, the following effects can be achieved. .

(a) Since the read test is performed by writing test data using an actual code pattern method using an actual read/write head and circuit, the optimum write current is determined based not only on the characteristics of the magnetic recording medium but also on the data read/write characteristics of the device. By testing the overall characteristics, it is possible to set the value that best suits the actual situation of the magnetic disk storage device.

(b) By simply connecting a simple write current adjustment circuit and loading test software, it is possible to automatically perform an optimum write current test on the magnetic disk storage device itself during the mass production process.

(C) Since the test data is read even when the head is off-track, the data recording resolution of the magnetic recording medium can be accurately evaluated. Furthermore, since the test data is overwritten, it is possible to accurately evaluate the write current dependence of the overwrite characteristics of the magnetic recording medium.

(Environmental tests regarding 4 temperatures etc. can be performed relatively easily.

Note that this feature of the present invention is particularly effective in improving the quality control level of mass-produced magnetic disk storage devices.

[Brief explanation of drawings]

The drawings all relate to the present invention; FIG. 1 is a configuration circuit diagram illustrating a general configuration of a magnetic disk storage device embodying the present invention, FIG. 2 is a circuit diagram illustrating an example configuration of a write current adjustment circuit, and FIG. In figure 0, which is a flowchart illustrating the overall operation of the present invention, l: disk, 2 spindle motor, 2a: pulse generator, 3: head, 4: swinging arm, 5: actuator, 5a: actuator drive circuit. , 6; read/write circuit, 7: read signal demodulation circuit, 8: data separation circuit, 9
: Encoder/decoder circuit, 10: Data circuit, ll
: Built-in processor of magnetic disk storage device, 12: Internal bus, 13: Interface circuit, 14: External bus for total X1ll, 15: Communication bus, 16: Indicator light, 20: Off-track detection circuit, 30: Write current adjustment circuit, 31: high resistance, 32 to 34: low resistance, 35 to 37: low resistance short circuit switch, 4o: write current specifying means, 41 to 44: operation steps of write current specifying means, 50: head position control Means, 51-58: Operation step of head position control means,
6o: Test data writing means, 61 to 69: One operation step of test data writing means, 70: Reading test means, 71 to
77: Operation step of reading test means, 81 to 86: Operation step of processor, 90: Magnetic disk storage device,
C: Minimum number of reading errors, Cj: Number of reading errors, c-
2. Initial value of minimum number of reading errors, d: off-track amount,
δ: value to cause the head to off-track, da: target value for off-track amount, dd: deviation from off-track target value, d-: allowable limit for off-track amount, D
jsjth read data, oo: data to be erased, F: flag, R5: head selection command, i: current specification code, 5-: maximum value of current specification code, in: optimum current specification code, Ix: index pulse, j: test data number,
j-: Maximum value of test data number, R5: Read signal, R-
: read/write command, TD: test data, trout s: write signal.

Claims (1)

[Claims] 1) Predetermined test data is written while the data write current is kept at a predetermined value and the head is on-track on a track in the disk, and the head is on-track and off-track with respect to that track. The test data is read each time under the condition that the test data is read, the presence or absence of a read error is verified, and the sum of the number of read errors is stored in correspondence with the write current, and the write current is changed within a predetermined range to write. An optimal write current testing method for a magnetic disk storage device, characterized in that a write current corresponding to the lowest number of read errors stored for each current is selected as the optimal write current. 2) An optimum write current testing method for a magnetic disk storage device according to claim 1, wherein test data is written by overwriting after writing of predetermined data. 3) a write current adjustment circuit that adjusts a current value for writing data to a track in the disk via the head; a write current specifying means that specifies a write current to the write current adjustment circuit;
A head position control means capable of controlling the position of the head relative to the track, and a test data write for writing predetermined test data with a write current specified by a write current specifying means while the head is on track by the head position control means. The recording means and the head position control means move the head on-track and off-track with respect to the track on which the test data has been written, read the test data each time, and count the number of reading errors while verifying the presence or absence of reading errors. and read test means for storing the sum of the number of read errors, and each time the write current specifying means switches the write current of the test data, the read test means memorizes the sum of the number of read errors. 1. An optimum write current testing device for a magnetic disk storage device, characterized in that a write current corresponding to the lowest value among them is selected as the optimum write current.